The change to his passive was actually massive. They doubled the duration of his passive which is where most of Ryze's power is located. It used to only last 3 seconds pre 6 and for this reason he was fairly weak in the early game and even the midgame, by the time he was at 6 seconds on his passive, it was lategame teamfighting time and Ryze was typically underpowered for those fights because his early game was pretty bad.
The way it works now is that Ryze has the same spell output potential that he had at lvl16, in lane this is pretty abusive when you max W first and you perma snare your opponents. If you had done this with Ryze's old passive duration, you would still be able to root someone a few times, but it was only a 4 second duration at level 6, meaning you couldn't bully your opponent as hard in the early game, which is where Ryze shines right now. His midgame became better because he could basically solo kill anyone who doesn't respect Ryze's 600 range W while in lane, and he still has a strong lategame potential due to his high DPS.
All it took was the duration of his passive being increased to make him abusive. He was kept down in lane before because his passive didn't last long enough to get out enough damage to mean enough to your opponent. You could trade with his passive and get a favorable trade even, but you would not be able to nearly 100-0 someone at level 3 because you could snare them every 2 seconds and then cycle through your spells multiple times. It would go more like use W to proc passive, QEQ, W them again Q and then your passive is down.
---Right now your all in goes W proc passive QEQWQEQWQEQW passive is now down QE chase a little Q..W..QEQWQEQW. Basically either you run out of mana or they're dead by that time (usually it's the latter). And usually it happens before your passive is procced the second time.
He used to have a weak early game, but now his early game is insanely strong with little counterplay. I really don't know how this got past the PBE, but it makes me sad because now Ryze is going to get nerfs to his abilities (notably his W) and I'm afraid they aren't going to be enough and he will get nerfed again and basically he will end up a shell of his former self. I like Ryze. He has been one of my favorite champions and I was pretty happy with his rework. I'm upset that he ended up being broken after his buffs, as I thought he needed buffs in other areas to gradually bring him up to a strong spot rather than a huge buff that put him over the top. I personally would like a full revert of the passive duration change, but it has already been announced that his W is going to be hit in it's duration and probably it's cooldown. We'll see what happens. Sorry if I ranted a little bit, but I hope I was clear enough on how the buffs affected Ryze.
